ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
475 
He proposes to break up the present division of the Entomostraca 
into three sub-classes and to regard the present group of Malacostraca 
as a fourth sub-class ; set out in systematic fashion Prof. Grobben’s 
classification is as follows : — 
Class Crustacea. 
I. Sub-class Phyllopoda. 
1. Order Euphyllopoda. 
2. „ Cladocera. 
II. Sub-class Estheriasformes. 
Order Ostracoda. 
III. Sub-class Apodiformes. 
1. Order Copepoda. 
2. „ Cirripedia. 
IY. Sub-class Malacostraca (Branchipodiformes). 
A. Leptostraca. 
Order Nebaliidse. 
B. Eumalacostraca. 
1. Order Stomatopoda. 
2. „ Thoracostraca. 
3. „ Arthrostraca. 
This classification is very similar to one suggested by the late Prof. 
Balfour. 
Finally, with regard to the Malacostraca, the author propounds a 
phylogenetic table in which he derives the primitive Malacostraca from 
the primitive Phyllopoda ; a side branch leads to the Leptostraca, while 
the trunk is continued into the primitive Schizopoda. The lowest side 
branch gives off the Stomatopoda, the next the Amphipoda, Isopoda, and 
Tanaida, the next Cumacea, and the next the Decapoda, while at the top 
of the main trunk there stands the group Schizopoda. 
Protective Functions of Skin.* — Mr. W. B. Hardy has investigated 
the reason of Daphnia being such a “ conspicuously clean Crustacean,” 
while Cyclops has a host of ectoparasites. He studied the ectoderm of 
Daphnia after treatment with methylen-blue ; the animal was placed on 
a Microscope in a drop of normal salt solution, lightly coloured by the 
addition of a small quantity of the pigment. The preparation was then 
covered by a cover-glass, which was so supported by a few slips of 
moistened paper that it just touched the animal. On very lightly 
pressing the cover-glass with a mounted needle the brittle cuticle of the 
upper half of the shell is ruptured, and a crack 1/10 mm. long is made, 
by means of which the pigment slowly makes its way ; a most beautiful 
differential staining occurs, the various histological elements coming 
into view one by one as the stain penetrates further and further from 
its point of entrance. 
The cells of the ectoderm are seen to be, for the most part, thin and 
plate-like in character, and each corresponds in size and shape to a 
superjacent area of the pattern on the carapace. In addition to the flat 
cells there are others which are thicker, and bear processes which 
extend into the seta-like hairs which form a fringe to the free edges of 
* Journal of Physiology, xiii. (1892) pp. 309-19. 
